In patients who require total parenteral or enteral nutrition the intestinal lining may atrophy and the ability to absorb nutrients may be lost. To prevent atrophy of the small intestine, we administered a suspension of Clostridium butyricum to elderly patients receiving tube feeding, and then measured the activation of serum diamine oxidase and the number, form, water content, and bacteria content of stools, indicators of intestinal structure. We found a significant increase in diamine oxidase activity and an improvement in stool condition: the number of stools per day decreased, form improved, and water content and the number of aerobic bacteria decreased significantly. These results indicate that in patients receiving long-term tube feeding, administration of Clostridium butyricum can restore condition to a near-normal state.